The U.S. economy expanded at a 2.2 percent annual pace in October, November and December of 2014, which is much slower than growth in the previous quarter. Consumers, meanwhile, grew a bit less optimistic in March.

A government report issued Friday says lower federal spending and rising imports restrained U.S. growth at the end of last year.

The analysis is a final revision of the fourth-quarter growth figures, based on the most complete data. The figures surprised many economists who had predicted slightly higher growth for those three months.

The report also shows the growth rate for all of 2014 to be at 2.4 percent, which is a little faster than the previous year.

The gross domestic product, or GDP, is the broadest measure of economic health and tracks all the goods and services produced in the nation.

Economists say growth in the first few months of this year may have been hurt by unusually foul winter weather and the strong dollar. The rising value of the dollar means U.S.-made goods are more expensive on global markets, which can hurt exports.

The value of exports is added to the GDP, while the cost of imports is subtracted to the assessment of economic activity.

Meanwhile, a separate study by the University of Michigan showed that consumers were a little less optimistic in March, as foul winter weather cut working hours for some people and gasoline prices rebounded slightly. Economists and investors watch consumer attitudes closely because consumer demand drives most U.S. economic activity.

Investment adviser Martin Leclerc said the overall decline in oil prices would eventually boost consumer confidence and spending.

He said that when prices first dropped, beleaguered consumers saved the money they did not spend on gasoline. Leclerc, of Barrack Yard Advisors in Bryn Mawr, Pennsylvania, said consumers would soon start feeling a little wealthier, saving a little less and spending a little more, which will help economic growth.